Web browser-based email services are widely used for communicating information over the Internet. Besides the information in its message body, an email message often includes attachments of various document types. These attachments provide a recipient of the email message additional information in connection with the message body. To view the content of an attachment, the recipient of the email message typically downloads the attachment to a client computer and then launches a native application program to open the attachment because web browser-based email services are typically unable to display email message attachments other than HTML, text and image attachments within a web browser window. This traditional approach to viewing email message attachments is inconvenient, because downloading the attachment and launching the application are often time consuming operations. In addition, if the client computer does not have an application program to open the attachment, the message recipient is unable to view the attachment, even if it is successfully downloaded to the client computer.